1. Field of the Invention
The present invention relates to a sheet conveyor that comprises a conveying path along which a sheet is conveyed, a transparent member disposed on the conveying path and facing the sheet being conveyed, and a guide member disposed upstream of the transparent member in a conveying direction of the sheet and guiding the sheet to the transparent member. The present invention also relates to an image reading apparatus comprising such a sheet conveyor.
2. Description of Related Art
Facsimile, copier, and scanner devices equipped with automatic document feeders (which hereinafter are referred to as ADFs) are known. An ADF conveys documents sequentially along a conveying path extending between a feed tray and a catch tray and allows each document to face a contact glass plate in the course of the conveying process. An image sensor is disposed at a position corresponding to the contact glass plate. Such an image sensor reads an image on a document conveyed thereto through the contact glass plate. Such a document-conveying process in an ADF is achieved by means of a sheet conveyor.
In such a sheet conveyor, a guide is configured to smoothly guide a document to the contact glass plate. For example, in Japanese Unexamined Patent Application Publication No. H10-139211 A, guiding means elastically nip a document from above and below. In Japanese Unexamined Utility Model Application Publication No. H04-29543 U, a brush is pushed down by a conveyed document and extends across the boundary between the document and a contact glass plate. In Japanese Unexamined Patent Application Publication No. H01-162651 A, a guide member is held at a predetermined, adjacent position and faces a contact glass plate.
When a guide is disposed upstream of a contact glass plate in the conveying direction, a certain step is formed between the guide and the contact glass plate to achieve higher assembly precision and to allow the leading end of a document to be conveyed smoothly. Nevertheless, when the trailing end of a document passes over this step, the document tends to behave in a specific manner. For example, when the trailing end of a document drops from the step onto the contact glass plate, the impact may cause such a specific behavior to occur on the document. Such behavior by the document may reduce the quality of an image read through the contact glass plate. Such reduced quality of a read image occurring due to the specific behavior by the document also is referred to as a specific reading defect.